Diagnostic system and method for metallurgical reactor cooling elements

ABSTRACT

Diagnostic methods and systems are used to determine operating condition and performance of a cooling element in a metallurgical reactor during operation of the reactor. The system can include sensing means, processing means and display means. The sensing means is located in or approximate the cooling element for sensing operating conditions of the cooling element. The processing means is in communication with the sensing means for receiving data corresponding to the sensed operating conditions and for processing the data to determine a relative condition indicator of the cooling element. The display means is in communication with the processing means and displays the relative condition indicator to a user of the diagnostic system. The display means can display a first, second or third state representative of the relative health indicator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/460,805 filed Jul. 28, 2006 now U.S. Pat. No. 7,976,770 and claimsthe benefit of U.S. Provisional Patent Application Ser. No. 60/703,430filed Jul. 29, 2005 and U.S. Provisional Patent Application Ser. No.60/720,457 filed Sep. 27, 2005, the entire contents of all of which arehereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to diagnostic systems andmethods for metallurgical reactor cooling elements. In particular, theinvention relates to diagnostic systems and methods for determining theperformance and condition of such cooling elements in real time duringthe operation of the reactor.

BACKGROUND

Some metallurgical reactors employ cooling elements to conduct heat awayfrom refractory linings in order to provide the safe containment andhandling of molten slags, mattes, metals, and fused salts. The coolingelements are manufactured of a high thermal conductivity solid havinginternal channels through which is pumped a cooling medium for thepurpose of extracting heat from the refractory lining by the coolingelement. When sufficient heat is extracted by a cooling element, it ispossible to maintain some thickness of relatively cool refractory orfrozen (i.e. solidified) process material in the area of the coolingelement. This is important for providing the necessary integrity for thesafe containment of molten materials.

The solid material making up the cooling element may typically be copperand the cooling medium is typically water, though other solid materialsand cooling media can be used. Such metallurgical reactor coolingelements may include, for example, a copper cooler built into thesidewall of the reactor or a tapblock for removing (or tapping) themolten process material from the reactor.

Cooling elements may comprise a cast rectanguloid copper block withinternal channels to allow for the flow of the cooling medium, withrefractory material placed between the cooling element and the moltenprocess material in the reactor. The internal channels are typicallypipes that are cast into the copper block during manufacture, that areexternally connected to the system providing the cooling medium.

Tapblocks are a variant of a typical cooling element, in that there is achannel through the center of the cooling element lined with arefractory material through which the molten process material flows whenthe reactor is being tapped. The center channel is typically of smalldiameter, such as 1 to 4 inches, and is plugged with a hard claymaterial when it is not required to tap molten process material from thereactor. In order for the reactor to be tapped, the clay plug in thetapblock must be removed by drilling or lancing, or a combinationthereof, so as to open the channel and allow the molten process materialto flow out of the reactor.

Typical operations for a reactor, including tapping, result in thecooling elements experiencing thermal and mechanical stresses that maycause the condition of the cooling element to deteriorate with time, ineffect reducing its ability to extract heat from the reactor. This isundesirable as it reduces the level of reactor integrity and safetyprovided by the cooling elements. If the cooling element performance isdeteriorated below an acceptable safety limit, maintenance is required.Major maintenance may involve shutting down the reactor to replace partor all of the refractory in the tapping channel of a tapblock orreplacing the complete tapblock, for example. Major maintenance ofcooling elements is generally expensive and time consuming, and the timebetween major maintenance should be extended as long as possible.

In order for operators of the reactor to assess the current operatingcondition of the tapblock, the temperature and cooling media flow incertain parts of the cooling element may be monitored, for example, bytemperature and flow sensing instruments distributed in and around thecooling element. Simulation by computer modeling in the design phase ofthe cooling element, using, for example, finite difference methods, maydetermine the expected temperatures and temperature profiles at thetemperature sensing instrument locations.

Using computer models, alarm levels may also be established for each ofthe temperature and flow sensing instruments to determine whether thecooling element is currently experiencing temperatures or cooling mediaflows that are beyond what was expected during the design stage.

Such modeling involves comparing the temperature and flow readings ateach sampled instant in time with pre-defined alarm levels. Generallytwo different alarm severities are available, denoted by Hi and HiHi (orLo and LoLo for coolant flow). The Hi alarm is primarily a notificationto the operator that the temperature is above the expected normaloperating range. This alarm does not necessarily require any remedialaction to be taken. The HiHi alarm indicates that the reactor may beexperiencing damaging or dangerous temperature levels. If the HiHi levelis exceeded, some automatic action may occur, like tripping the reactorbreaker to remove power input and starting the process of reducing thetemperature of the process material.

These temperature and flow alarms only provide an indication oftemperature or flow excursions outside of what is considered desirable,and do not distinguish between the different particular conditions thatcould cause a temperature excursion, such as refractory wear, highprocess operating temperatures, or the deteriorating thermal ormechanical performance of the cooling element.

The described embodiments seek to address or ameliorate one or moreshortcomings or disadvantages associated with existing means and methodsof assessing the condition of a metallurgical reactor cooling element.

SUMMARY

Embodiments of the invention generally relate to diagnostic methods andsystems for determining the operating condition of a cooling element ina metallurgical reactor during operation of the reactor.

Certain embodiments of the invention relate to a diagnostic system for acooling element, the system comprising:

at least one sensor located in or proximate the cooling element forsensing operating conditions of the cooling element;

at least one processor in communication with the at least one sensor forreceiving data corresponding to the sensed operating conditions and forprocessing the data to determine a relative condition indicator of thecooling element; and

at least one display in communication with the at least one processorfor displaying the relative condition indicator to a user of thediagnostic system.

In one embodiment, the at least one display comprises a display portionfor displaying a first, second or third state representative of therelative condition of the cooling element. The first state maycorrespond to an operational state of the cooling element, in which thecooling element may be operated normally, the second state maycorrespond to a cautionary operational state of the cooling element, inwhich the cooling element should be operated under caution, and thethird state may correspond to a non-operational state of the coolingelement, in which the cooling element should cease operation or notinitiate operation.

By monitoring the at least one sensor and performing diagnostics withthe information provided, metallurgical reactor operators may beprovided with an indication of whether or not the reactor equipment isbeing operated within its design constraints or in a way that wouldreduce the safe operating life of the cooling element. The indicationmay be provided by, for example, an indicator having Green, Yellow andRed (GYR) lights to resemble a traffic light. The green light mayindicate, for example, that the cooling element is being operated withinits designed operating conditions. The yellow light may indicate, forexample, that one or more operating conditions is not being met or isoutside the normal operating range and that attention to the coolingelement or instruments is required. The red light may, for example,indicate that the cooling element is being operated substantiallyoutside the normal operating range and should not be used further untilthe cause of the condition is investigated and resolved.

Alternatively, or in addition to display of the first, second or thirdstate, the relative condition indicator may include a numerical orgraphical representation of the relative condition of the coolingelement on the at least one display.

The relative condition indicator may in part represent the long-termwear of the cooling element. The long-term wear may be determined atleast in part by determining an area condition for each of a pluralityof areas of the cooling element. The overall cooling element long-termwear may be determined at least in part by the lowest or highestdetermined area condition.

Other embodiments of the invention relate to a method for providing arelative condition indication of a condition of a cooling element. Themethod comprises sensing operating conditions of the cooling element;receiving data corresponding to the sensed operating conditions andprocessing the data to determine a relative condition indicator of thecooling element; and displaying the relative condition indicator to auser.

Further embodiments of the invention relate to a computer readablestorage having stored thereon computer program instructions, which, whenexecuted by a computer system, cause the computer system to perform thefollowing steps: receiving data corresponding to sensed operatingconditions of a cooling element; processing the data to determine arelative condition indicator of the cooling element; and displaying therelative condition indicator to a user.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in further detail below, byway of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a block diagram of a diagnostic system for a metallurgicalreactor, according to one embodiment of the invention;

FIG. 2 is a block diagram of one embodiment of the diagnostic system ofFIG. 1, showing a diagnostic computer system in further detail;

FIG. 3 is a perspective view of a tapblock cooling element, showinginstrument locations in the tapblock;

FIG. 4 is a graph showing typical temperature characteristics sensed bya thermocouple in a tapblock cooling element during pre-tapping, tappingand post-tapping operations;

FIG. 5 is a flowchart of a method of determining a relative healthindication of a cooling element;

FIG. 6 is a flowchart of a second method of determining a relativehealth indication of a cooling element;

FIG. 7 is a flowchart of a method of monitoring a cooling element;

FIG. 8 is a chart of an example Principal Component Analysis (PCA) for atapping procedure;

FIG. 9 is a block diagram of another embodiment of a diagnostic systemfor a metallurgical reactor; and

FIG. 10 is an example chart relating the Principal Component Analysis(PCA) to the operating condition of a tapblock cooling element.

DETAILED DESCRIPTION

The described embodiments relate generally to diagnostic systems andmethods for metallurgical reactor cooling elements. In particular,embodiments relate to diagnostic systems and methods for determining thecondition and performance of cooling elements in real-time duringoperation of the reactor.

While it should be understood that embodiments can be applied to variouskinds of elements requiring diagnostic analysis of their conditionwithin a larger apparatus, the described embodiments have particularlyuseful application to automated diagnostic analysis of tapblock coolingelements in a metallurgical reactor. The described embodiments also haveparticularly useful application to other cooling elements, such ascopper coolers located in the walls, roof, or other areas of a reactor.For ease of illustration, the embodiments are described primarily inrelation to their application to diagnostic analysis of tapblock coolingelements. An example tapblock cooling element is shown in FIG. 3.

In the drawings and in this description, like reference numerals will beused to indicate like elements, functions or features as between thedrawings and the described embodiments.

One embodiment of the invention is shown in FIG. 1, in the form of adiagnostic system 100 for a metallurgical reactor 110. The metallurgicalreactor 110 has a plurality of tapblocks 120 for tapping molten materialfrom the reactor 110. The reactor 110 may have two tapblocks 120 asshown in FIG. 1, or it may have more tapblocks, for example for drainingslag from the top of the reactor bath, as well as for drawing moltenprocess material from lower levels. In some instances, the reactor maybe run using only one operational tapblock 120.

Each tapblock 120 has a number of instruments 125 associated therewith,either located in the tapblock or nearby, for measuring the operatingconditions of the tapblock 120. Such instruments include thermocouples,resistive temperature devices (RTDs) and flow meters, at a minimum andmay include further instruments for measuring other process conditions.

Diagnostic system 100 comprises a diagnostic computer system 130, theinstruments 125, a status display 140 and a plurality of user stations160 connected to diagnostic computer system 130 over a network 150, suchas an Ethernet control network. Diagnostic computer system 130 receivesmeasurement data from instruments 125 and determines whether thetapblocks 120 are in a suitable condition for normal operation in theshort term and determines a longer-term projection of the health of thetapblock. Use of the term “health” in this context is intended toindicate the relative condition and ability of the tapblock (or othercooling element) to perform its function properly and safely. Similarly,“health index” is intended to be an indicator of relative condition,wear and/or operability of the cooling element. Such an index can alsobe called a “wear index” or a “condition index.”

Diagnostic computer system 130 provides an output to status display 140for local indication of the operational status of the tapblocksindependently of the connection to network 150. This operational statusis also provided by diagnostic computer system 130 to user stations 160for consideration by plant personnel situated away from the reactor 110.At least one such user station 160 may be located nearby the reactor 110in order to provide a user interface to the diagnostic computer system130 for use by a reactor operator stationed nearby reactor 110. Althoughnot shown, diagnostic computer system 130 has a suitable user interfacefor receiving user input and providing output to the user.

Status display 140 provides a highly visible display positioned nearreactor 110 to indicate the operational status of each of the tapblocks120. The operational status is preferably indicated by one of threepossible state indicators. The state indicators indicate an operationalstate, a cautionary state and a non-operational state. These states maybe respectively indicated by green, yellow and red lights on statusdisplay 140 so as to resemble common traffic signals. Alternatively,other readily recognizable visual indicators can be used as the stateindicators. Thus, for a reactor operator positioned near the reactor110, status display 140 provides a ready indication of the operationalstatus of tapblocks 120 and allows the reactor operator to takeappropriate action according to the indicated status.

Referring now to FIG. 2, diagnostic computer system 130 is shown infurther detail in the context of diagnostic system 100 of FIG. 1. Asshown in FIG. 2, instruments 125 associated with tapblocks 120 includethermocouples 210, RTDs 220 and flow meters 230. Other forms oftemperature and/or flow measurement instruments can be used instead, orin addition to, those shown. Each of these instruments 125 provides itsanalog output (corresponding to the relevant process variable measuredby the instrument) to an analog to digital converter 240. The analog todigital converter 240 may be integrated with or co-located with thediagnostic computer system 130 or may be distinct and/or remotetherefrom.

Diagnostic computer system 130 comprises computer software 205 stored ina memory 208 and executing on one or more computer processors (notshown) to perform the diagnostic function of diagnostic system 100 ofFIG. 1. Computer software 205 comprises a plurality of software modulesfor processing the data received from instruments 125 (which includeinstruments 210, 220 and 230). Such software modules include a dataintegrity module 250, a data processing module 260, a diagnostics module270 and a reporting module 290. Diagnostic computer system 130 furthercomprises a database 280 for storage and retrieval of diagnostic datagenerated by computer software 205 based on the received instrumentdata. Although computer software 205 is described as comprising softwaremodules, some or all of the functions of the software modules may beexecuted in hardware. As an example, open circuit detection (describedbelow) can be detected using software algorithms or by the hardware ofthe analog input card that the instrument is connected to. Analternative diagnostic system embodiment, designated by reference number900, is shown and described later in relation to FIG. 9.

For ease of explanation of the functions and interactions of the variouscomponents of diagnostic systems 100 and 900, specific features andfunctions of instrumentation will be described first, followed by adescription of specific features and functions of the software modulesin computer software 205.

Instrumentation

For a reactor element such as a tapblock or a copper cooler,thermocouples 210 must be positioned so as to have their sensingjunctions located as close as possible to the point at which the desiredtemperature is to be measured. FIG. 3 illustrates an example tapblockand shows example cooling conduit and thermowell configurations.

It is important to have the time constant (the time it takes for theinstrument reading to reflect a change in process conditions) of thethermocouples and RTDs as similar as possible because some of thesubsequent analysis, for example, such as the Principal ComponentAnalysis, involves comparing the time response of the outputs of thethermocouples and RTDs.

As illustrated in FIG. 3, the tapblock is roughly rectanguloid and has aroughly cylindrical tapping channel running through its centre. Thetapping channel is normally lined with refractory material, which comesinto contact with the molten process material during tapping and whichshields the copper block from damage. One side of the tapblock isdesignated as the “hot face”, as it faces toward the inside of themetallurgical reactor. The opposite face of the tapblock is the tappingside.

The tapblock in the illustrated example includes two water-coolingcircuits (A and B) for passing cooling water through the tapblock toremove heat therefrom during tapping. The water cooling circuits havethe RTDs (or other suitable temperature sensors) positioned in relationthereto for sensing the inlet and outlet water temperatures for eachcooling circuit. The water cooling circuits are provided by cast-inpiping that circles the cylindrical tapping channel and passes alongareas of the hot face.

The tapblock illustrated in FIG. 3 also includes thermowells positionedto receive thermocouples at appropriate locations for taking the desiredtemperature measurements.

Good standard instrumentation engineering practice for grounding andshielding of instrumentation cables must be used to ensure that clean,low noise signals are available to the diagnostic system. In addition,the area around a furnace is a harsh environment with high temperaturesand there is a possibility of splashing molten process material or slag.The instrument arrangement including cabling must be carefully designedto survive in such an environment. Cable and instrument thermal shieldsare often required to protect the equipment.

For improved reliability and availability, dual instruments can be usedwhere two individual thermocouples or RTDs are installed at the samelocation, thus providing a redundant measurement. For example, dual RTDsmay be used to measure a reference water temperature, such as the inletwater temperature, because this reading is used as a basis forsubsequent analysis like the temperature-based wear index. Also, thereare no opportunities to estimate the reference water temperature fromother temperature readings without affecting the accuracy of thesubsequent analysis.

Dual insert thermocouples are used because the insert thermocouple (whenavailable as part of the tapblock design) is used to provide anindication of the start and end of tapping. An insert thermocouple isthat which is in the refractory material closest to the tapping channel.Analysis of the readings from the redundant instruments allows faultyreadings to be detected by comparing the data from the two instruments.If both instruments are functioning correctly, the readings from bothinstruments will be substantially the same, whereas if one of the twoinstruments is faulty, the readings from the two instruments willdiverge.

In addition to the thermocouples and RTDs, additional high-resolutiontemperature readings can be obtained using optical techniques thatinvolve inserting a fiber optic cable positioned in the water passage(or with suitable protection cast in the copper or inserted in therefractory) of the tapblock and directing light of predeterminedwavelengths along the fiber. Two techniques that can be used to measuretemperature based on the characteristics of reflected light include: 1)Fiber Bragg Gratings and 2) Raman Back-scattering. Such techniques relyon the temperature dependence of light reflection by formations withinthe fiber. For application in a tapblock or reactor vessel coolingelement, the Bragg Grating appears to be the more appropriate optionbecause it would provide readings of about 0.1 degree accuracy atspacings of 10 cm and 100 or more reading sites would be available witha single fiber.

Shown in FIG. 4 is an example plot of temperature versus time, as sensedby an insert thermocouple in a tapblock shown in FIG. 3. The tappingcycle may be viewed as having four stages, denoted by A, B, C and D.Stage A denotes a period prior to tapping or after tapping, in which thetemperature in the tap block is relatively low and stable. Once atapping operation is initiated, the number of the tapping operation istracked for recording and maintenance purposes and the rate oftemperature increase is measured.

The period during which the temperature increases is designated as stageB. The rate of increase of temperature during stage B is monitored andrecorded. Once the level of the increased temperature stabilizes and isrelatively constant, the tapping operation is considered to be in stageC. During stage C, the average temperature measured during tapping isrecorded, together with the maximum sensed temperature. Stage D occurswhen the tapping operation is stopped and the sensed temperature in thetapblock generally decreases. During stage D, the rate of decrease ofthe temperature is measured.

During, before and after the tapping operation, various measurements andstatistics concerning the tapping operation are gathered in addition tothose mentioned above. For example, the total tapping time is recorded,together with the temperature during stage A before and after tappingand the total time in which the temperature exceeded the Hi Alarm leveland HiHi Alarm level, if at all. If the temperature exceeded eitheralarm level, the amount by which the alarm level was exceeded is alsorecorded for diagnostic purposes, as described below.

Software Modules

Data integrity module 250 is responsible for analyzing the incomingsignals to determine whether the data being gathered is reliable bydetecting possibly faulty instrumentation. An instrument is flagged asfaulty if one or more of the following conditions is detected:

-   -   The signal is very noisy, indicating a bad connection. This is        detected when data integrity module 250 determines that the        standard deviation of the signal is above a predefined        threshold.    -   The signal is inactive. This indicates that there is a        communication problem between the analog/digital converter 240        and an instrument 125 or between the analog/digital converter        240 and the diagnostic system 130. Inactive signals are detected        if the reading from the instrument 125 remains unchanged for a        predefined period of time.    -   An open circuit is detected. RTDs usually employ a transmitter        that provides an output between 4 and 20 mA. An open circuit        condition is determined when no current is detected. For        thermocouples, an open circuit condition results in a high        temperature reading beyond the limit of measurement range. If a        reading right at the limit of the detection range for the analog        to digital converter is encountered, the thermocouple is        detected as open circuit.    -   High rate of change. This condition is triggered if an        instrument reading increases or decreases at a rate that is        beyond what is physically possible for the instrument, in which        case data integrity module 250 determines that the readings are        false readings.    -   For redundant instruments, if the two instruments do not provide        identical readings, the instruments are determined by data        integrity module 250 to be faulty.    -   Drift. There is a concern that over an extended period of time        instruments will drift out of calibration. Drift is detected by        examining the long-term trend of the data to detect a small but        steady positive or negative drift in the readings that indicates        a faulty instrument.    -   Thermocouples in copper cooling elements may experience a        “floating” condition. The term “floating” is applied to the        condition where a thermocouple is not touching the bottom of the        thermowell in which it is installed and this results in a        thermocouple reading lower than the actual copper temperature.        For example, in a copper element cooled by water flowing in        cast-in piping, the sources of heat are from the hot face        nearest the reactor bath and the tapping channel. The        thermocouple junctions are positioned between the water cooled        passage and one or more heat sources and as a result, the        thermocouple temperature reading should be between the water        temperature and the temperature of the heat sources. If the        measured thermocouple temperature is lower than the measured        water temperature the thermocouple is flagged as “floating”        because this condition is not physically possible.

If an instrument or its readings are flagged as faulty because of one ofthe conditions above, the expected value of the instrument can, in somecases, be re-constructed using the readings from adjacent instruments.In certain embodiments, the reconstruction is done using a neuralnetwork that is trained using data generated from computer modeling ofthe thermal behavior and characteristics of the tapblock. The use ofmodel data enables calibration of the reconstruction neural networks ofthe diagnostic system 130 during the design stage, before the diagnosticsystem 130 is installed for operation. Some calculations of diagnosticsystem 130, including Principal Component Analysis (PCA) calculations,require data from many instruments to function properly.

In alternative embodiments, the instrument value of the faultyinstrument can be reconstructed using the average or weighted average oftwo or more nearby instruments.

The use of re-constructed data advantageously enables the calculationsto be carried out even with a limited number of faulty instruments. Theneural network resides in (or is at least controlled by) data integritymodule 250 and includes a software process taking two or more inputs andproviding one output. The output is the estimated temperature readingfor the faulty instrument and the inputs are the temperature readingsfrom two or more adjacent instruments. The output of the process isgenerated using standard neural network algorithms, such as aredescribed in texts in the neural network field.

The data processing module 260 is responsible for calculating themetrics or extracting features of the measured temperature profiles foreach of the instruments that is providing valid temperature data. Thedata processing module 260 receives temperature readings from the dataintegrity module 250 and provides outputs to the diagnostics module 270and reporting module 290. FIG. 4 shows an example temperature profileanalysis that the diagnostic system performs.

The data processing module 260 includes algorithms to identify the startand end of tapping and assigns a unique identifying number to eachtapping event. The beginning and end of tapping are identified by thetemperature profile of a thermocouple physically located near thetapping channel (insert thermocouple) or by signals from a mudgun usedto open and plug the tapping channel. The tapping duration is determinedas the difference in timestamp between the start and end of tapping.Using a thermocouple near the tapping channel, the temperature rate ofchange and the temperature magnitude are sensed and used to indicate thestart and end of tapping. Alternatively, the combination of the mudgunposition in front of the taphole and the use of the mudgun drill alsosignify the start of tapping. The combination of the mudgun position infront of the taphole and an increase in mudgun pressure indicates theend of tapping. Appropriate position switches (not shown) and otherinstrumentation are used to indicate the position and use status of themudgun.

Statistics are generated from the measured data for each tap and aresaved in the database 280. Typical data that are extracted for each tapinclude the rate of increase at the start of the tap, the tapping time,the maximum temperature during the tap, the average temperature duringthe tap and the steady temperature before and after the tap. Thetemperature data gathered during the tapping operation and stored in thedatabase 280 can be used for further critical analysis of the tappingevents by software or by plant personnel.

The diagnostics module 270 is responsible for examining the data fromthe instruments to extract two main outputs: 1) the current operatingcondition of the tapblock, as displayed on display 140 and on userstations 160, for example as a traffic light (green, yellow and red);and 2) a health index that represents the long-term wear on thetapblock. For both the traffic light and the health index, thediagnostics module 270 provides supplemental outputs with supportinginformation related to the two main outputs.

The traffic light (green, yellow and red) indications serve to notifythe operator when conditions occur that are likely to reduce the life ofthe block or reduce the safety of the tapping operation. The color ofthe light is determined from a set of rules that are IF . . . THENstatements determined according to operational limitations, designexpertise and operational experience. The heuristic rule set may bemodified or re-configured depending on the modes of operation and asexperience with the specific tapblock is gained.

The most severe light color determined by any of the rules is displayedas the overall condition of the tapblock. If any of the rules thattrigger a yellow are active, the condition will be yellow. If any of therules that trigger a red condition are active, the condition will bered. Yellow takes priority over green and red takes priority over bothyellow and green. The overall status will be green only if no rules aretriggered.

All active rules are displayed on supplemental operator screens. Thepurpose of displaying the complete rule set is to provide guidance tothe reactor operators in determining the cause of the change incondition. For example, the displayed breached rule may indicate anunexpected temperature profile during tapping. The Rule-based diagnosticsystem also provides output to assist in the maintenance of the reactortapblock or cooling element. For example, a rule may relate to ascheduled refractory lining replacement on the tapping channel of thetapblock.

Some example rules include:

-   -   Too many taps since the last repair of the tapping channel        refractory bricks. The light is changed from green to yellow if        the number of taps since the last brick repair is greater than a        pre-configured number. The light will change from yellow to red        if a second higher number of taps is completed without        performing a repair. Tapping channels usually include several        layers of bricks that are numbered starting with layer one at        the cold face (outside of the furnace) of the tapping channel        and with higher numbers towards the inside of the furnace. Each        layer can have a different specified number of taps before a        repair is required and separate rules are used to track the        number of taps for each layer.    -   Shallow drill depth. If the depth that is drilled to open the        tapping channel is shallow (less than a predefined depth), the        light is changed from green to yellow. If the shallow drill        depth is experienced on multiple consecutive taps, the light is        changed from yellow to red.    -   To announce degradation of the tapblock health (described        below), a rule related to the tapblock health index is added to        the GYR indication. The GYR indication can be green for a health        index greater than 60%, yellow for a health index between 60%        and 30% and red when the health index is less than 30%, for        example. These threshold percentages are configurable and are        provided by way of example.    -   The time it takes to tap the reactor. The beginning and end of        tapping are identified by the temperature profile of a        thermocouple physically located near the tapping channel (insert        thermocouple) or by signals from a mudgun used to open and plug        the tapping channel. The tapping duration is determined as the        difference in timestamp between the beginning and end of        tapping. Using an appropriately located temperature sensor, such        as the insert thermocouple, the temperature rate of change and        the temperature magnitude are sensed and used to indicate the        start and end of tapping. The mudgun position (in front of the        taphole) and the use of the mudgun drill also signify the start        of tapping. The mudgun position (in front of the taphole) and an        increase in mudgun pressure also indicate the end of tapping.        The tapping duration or length of time to fill a ladle can be        used to determine an indication of the tapping channel size. The        traffic light is changed from green to yellow (or red) if the        tapping time is less than a pre-determined time, which would        indicate that the tapping channel is worn and has increased        substantially in size.    -   Large taphole diameter. If the measured taphole diameter is        larger than a predefined size, the traffic light will change        from green to yellow. A second even larger measured taphole        diameter will change the light from yellow to red.    -   Profile analysis, which examines the temperature profile for        each individual instrument and flags unexpected conditions. For        example, the traffic light would be changed from green to yellow        if the temperature after the tap did not return to the pre-tap        temperature within a pre-configured temperature margin in a        pre-configured amount of time. The rate of change and absolute        temperature readings are other profile features that are        examined, for example to determine the tapping duration as        described above.

Other rules are derived from performing Principal Component Analysis(PCA) on the data gathered from the tapblock instruments 125. PCA is atechnique that is used to reduce the amount of data recorded by manyinstruments down to a few principal components that characterize theprocess. In many processes, the instrument readings are highlycorrelated, with many instruments responding similarly to an event. Thisis true for a tapblock where all the thermocouples respond to tappingevents in a similar fashion.

When a Principal Component Analysis was run using numerically modelleddata (for example, by computational fluid dynamics (CFD)) for a newtapblock, it was determined that two components, labeled PrincipalComponent 1 and Principal Component 2 in the upper half of FIG. 8, weresufficient to represent the variation seen in the temperatures during atapping event.

The principal components have the following physical meaning whendescribing the behavior of the tapblock. The x-axis, or PrincipalComponent 1, is the overall average of the temperature measurements inthe block, and a shift in the positive x-axis indicates a generalincrease in block temperature. The y-axis, or Principal Component 2, canbe thought of as the overall difference of the temperature measurementsin the block, and a shift in the positive y-axis indicates a generalincrease in temperature in some areas of the block (say, the upper half)relative to other areas of the block (say, the lower half). Theprinciple component plot in FIG. 8 corresponds to sensed temperaturesduring a tapping operation, as illustrated with respect to stages A, B,C and D in the bottom half of FIG. 8.

As an illustration, consider a simple example where there is a tapblockwith only two thermocouples. Suppose that the two thermocouples indifferent locations in the block have identical temperature readings:T₁=T₂=T. Principal Component 1 describes the average of the twothermocouples:

$\begin{matrix}{P_{1} = {{\frac{1}{2}\left( {T_{1} + T_{2}} \right)} = {T.}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Principal Component 2 describes the difference between the twothermocouples:P ₂ =T ₁ −T ₂=0  Equation 2.

Consider the case where the temperature at each thermocouple increasesby 5° C. The average or Principal Component 1 would increase by 5° C.and there would be a shift in the positive x-axis on the PrincipalComponents plot. However, the difference between T₁ and T₂ remains thesame at zero and there would be no shift in the y-axis. Consider adifferent case where T₁ increases by 5° C. and T₂ decreases by 5° C.This time, the average or Principal Component one, remains the same andthere is no shift in the x-axis, but the difference between T₁ and T₂increases, and there is a shift in the positive y-axis.

The PCA represents the readings from all of the tapblock instruments (adozen or more) as heating and cooling cycles of only two components(Principal Component 1 and Principal Component 2) as shown in the upperpart of FIG. 8. Every point in the plot in FIG. 8 represents the processstatus (instrument readings) at a specific time as the tap is occurring.PCA calibration refers to the procedure to determine the contributionsof the individual readings to each of the components. For example, thecoefficients in equation 1 are ½ for T₁ and ½ for T₂.

FIG. 10 illustrates an example heating and cooling PCA profile fortapping with a new tapblock and an example PCA profile for a tapblockhaving high wear. The PCA plot is divided into regions that correspondto the green, yellow and red conditions of the tapblock. As the tapproceeds, the profile for the new tapblock is entirely within the greenregion and the GYR indication would remain green. The colored regions onthe plot indicate that the profile for a worn block will enter the redregion, indicating that tapping on that particular block should besuspended until further investigation is completed.

The second main output of the diagnostics module 270 is the tapblockhealth index. The health index starts at 100% for an optimally healthytapblock and, with wear, declines to 0%. This provides an indication ofthe long-term accumulated loss of health or wear of the tapblock. Twomethods of determining the health index are described below withreference to FIGS. 5 and 6.

FIG. 5 is a flow diagram of a method 500 of determining a relativecondition indicator, such as the overall health index. Method 500 isevent-based, in that it looks for sharp or gradual temperature changes.The method illustrated in FIG. 5 compares the temperature measurementsto predefined Hi (high) and HiHi (extremely high) temperature (spike)thresholds. The spike thresholds are dynamically altered, depending onthe measured reference (e.g. inlet) water temperature, to avoidregistering unnecessary spikes due to high cooling-water temperatures.Should the temperature measurement exceed the Hi threshold, an eventcalled a “temperature spike” is determined to have occurred andtemperature-related wear is attributed to the tapblock based on theactual temperature level above the threshold and the time duration abovethe threshold.

The dynamic spike alarm level for thermocouple x may be calculated byEquation 3:DynamicSpikeAlarmLevel_(x)=Hi_(x)+(InletWaterTemperature−N)where N is a predetermined nominal reference water temperature. N may beabout 40° C., for example, and may be set at a desired level to suitoperating conditions.

The following polynomial function (Equation 4) is used to accumulatespike wear for thermocouple x when that thermocouple exceeds its dynamicspike alarm level:

${{SpikeWear}_{x}\lbrack i\rbrack} = {{{SpikeWear}_{x}\left\lbrack {i - 1} \right\rbrack} + {K\frac{\left( {{Temperature}_{x} - {DynamicSpikeAlarmLevel}_{x}} \right)^{PolynomialFactor}}{\left( {{HiHi}_{x} - {DynamicSpikeAlarmLevel}_{x}} \right)^{PolynomialFactor}}}}$where i represents time increments and K is a weighting factor betweenone and zero. The time increments may be about 1 second, for example. Anexemplary polynomial factor of about 5.5 is considered suitable. Thepolynomial factor and the weighting factor may be modified or fine-tunedbased on experience.

The spike wear at each thermocouple location is accumulated to calculatean area health index for the area adjacent to each thermocouple. Theoverall block health index is based on a selection of one or more of theindividual area health indices for the block. For example, the minimumarea health index can be taken as the overall health index.Alternatively, the overall block health index may be determined as anarea weighted average or based on a selection of area health indicesaround the minimum area health index. If the temperature exceeds the“HiHi” level in any area, the health index is set to zero.

Method 500 begins at step 505 by determining the Hi and HiHi thresholdlevels for a nominal inlet water temperature, such as 40° Celsius. Thenominal inlet water temperature may be calculated based on normaloperating conditions or may be chosen by the realtor operator. At step510, the actual inlet water temperature of the water cooling conduits issensed using RTDs 220. At step 515, the Hi and HiHi temperaturethresholds are calculated for the actual sensed inlet water temperature,based on the thresholds determined at step 505 for a nominal inlet watertemperature. This calculation is performed using Equation 3 to determinewhat is, in effect, a dynamic alarm level for each thermocouple.

Concurrently with steps 510 and 515, step 520 is performed, at which thetemperature is sensed in areas of the cooling element using the variousinstalled thermocouples. If, at step 525, any of the temperatures sensedat step 520 exceed the HiHi threshold dynamically determined at step515, diagnostics module 270 sets the overall health index to zero atstep 530 and a red condition will be triggered, in which operation onthe specific tapblock should cease until major maintenance can occur. Ifnone of the sensed temperatures is greater than or equal to the HiHialarm level, it is determined at step 535 whether any of the sensedtemperatures is greater than or equal to the Hi alarm threshold. If theHi threshold is not exceeded, the diagnostic computer system 130determines, at step 540, that no action is required, and to continuemonitoring, in which case steps 510 to 525 are repeated.

If at least one of the sensed thermocouple temperatures is above the Hithreshold, then at step 545, diagnostic module 270 determines the wearto be attributed to the respective areas of the cooling element forwhich excessive temperatures were sensed. The determination of step 545is made using Equation 4 for each time increment i during which the Hithreshold is equaled or exceeded by the respective sensed temperature.The accumulated wear attributable to the temperature spike for eachaffected area is determined at step 550. At step 555, the new overallhealth index is determined, based on the new area health indicesdetermined at step 550. Steps 510 to 555 are performed repeatedly and atregular intervals to re-calculate a new overall health index asnecessary. During a tapping procedure, steps 510 to 555 may be repeatedmore often than at other times.

In addition to the temperature event-based health index determination,the diagnostic computer system 130 makes the condition-based healthindex determination according to a method 600 illustrated in FIG. 6,which involves estimating the physical condition of the tapblockcomponents from the temperature and flow measurements. The physicalcondition may be defined, for example, by how well the cooling pipes arebound to the copper block, the physical characteristics of the copperblock and the thickness of the refractory.

The method 600 begins at step 605 by sensing the inlet water temperaturefor the cooling circuits and the flow rate of the cooling fluid. At step610, the heat flux for each of a number of sections or areas of thecooling element is determined according to existing heat fluxcalculation techniques. At step 615, the temperature in each specificarea of the cooling element is sensed. Any reconstruction of faultytemperature values may be done at this point. For diagnostic purposes,the cooling element is volumetrically divided up into specific areas inorder to calculate a health index specific to each area.

At step 620, the tube bond condition, expressed as thermal conductionresistance, is calculated from the temperature readings at thethermocouple locations, the inlet water temperature and the heat fluxcalculated using the water circuit flow and temperature rise. It may benecessary to temporarily reduce the water flowrate to get an accuratemeasurement of the tapblock heat flux. Using well-known equations forheat transfer, a thermal resistance is determined from the heat flux andthe difference between the copper block temperature and watertemperature. Using other well-known equations for heat transfer, thethermal resistance is converted into an equivalent thermal conductionresistance.

The refractory thickness adjacent to each thermocouple is calculated atstep 625 using equations derived by curve fitting the graphical resultsfrom a 3-dimensional CFD model or another numerical modeling method. Theequations have two inputs: 1) the thermal conduction resistance of thetube bond; and 2) the maximum thermocouple temperature measured duringtapping normalized to a standard water temperature and a standard moltenprocess material temperature.

The extrapolated copper tip temperature that would occur with highprocess temperatures is calculated at step 630 for each area of thetapblock from the tube bond thermal conduction resistance and refractorythickness. The copper tip temperature is the temperature of the copperblock nearest the inside of the furnace or hot face. To calculate thecopper tip temperature, a second set of equations is developed from theCFD (or other numerical) model that has two inputs: 1) the thermalconduction resistance of the tube bond; 2) refractory thickness. Theextrapolated copper tip temperature is the temperature that would occurunder high process temperature conditions; there is no need for anactual temperature spike to occur to reduce the area health index.

For each hot face and refractory area, a health index is calculated, atstep 635, from the estimated refractory thickness (a linear function isused starting at 100% at new refractory thickness and going to 0% at theminimum acceptable refractory thickness) and extrapolated copper tiptemperature (a linear function is used starting at 100% for theextrapolated copper tip temperature for a new tapblock with newrefractory and tube bond condition and going to 0% with the extrapolatedcopper tip temperature at the minimum acceptable refractory thicknessand poor tube bond condition).

An area health index is calculated at step 640, for example as theminimum of either the refractory thickness health index or theextrapolated copper tip temperature health index. The minimum is oneexample of calculating the area health index; other ways of combiningthe refractory thickness and copper tip temperature health indices intoan area health index are also possible, such as averaging or weightedaveraging.

The overall block health index is calculated at step 645 by combiningthe area health indices (for example, the lowest area health index canbe taken as the overall health index). The “condition-based” and“spike-wear” health indices can both be displayed or combined into asingle health index, for example by taking the average of the two.Following step 645, method 600 may be repeated regularly orcontinuously, as part of the diagnostic monitoring functions ofdiagnostic system 100 or 900.

Referring now to FIG. 7, a method 700 of monitoring a cooling element isshown and described. Method 700 begins at step 705, in which an overallhealth index of the cooling element is determined. Step 705 maycorrespond to performance of method 500 or 600 or both concurrently orin sequence. Once diagnostics module 270 determines the overall healthindex, it compares the overall health index to the cautionary thresholdat step 710. If the overall health index is above the cautionarythreshold, no specific action is required and the diagnostic system 100or 900 continues the diagnostic monitoring at step 720.

If the overall health index is below the cautionary threshold, thediagnostics module 270 determines at step 730 whether the overall healthindex is also below the emergency threshold. If it is not, plantpersonnel are alerted to the cautionary (yellow) status of the coolingelement and are notified that operation of the cooling element maycontinue under caution, at step 740.

If the overall health index is below the emergency threshold at step730, the health index is set to zero at step 750 and plant personnel areimmediately notified of the emergency (red) status. Notification of thecautionary and emergency status is performed through reporting module290, which provides a light (e.g. green, yellow or red) and/or graphicsdisplay on status display 140 and on displays associated with userstations 160. System 100 or 900 may automatically initiate proceduresfor shutting down the metallurgical reactor or ceasing the tappingoperation, if appropriate, or may await an operator command to do so.

The reporting module 290 is responsible for displaying the results ofthe rule-based traffic light and the health index. The results aredisplayed to the operator using display 140 and on user stations 160.Beyond the final overall results of the traffic light and the healthindex, the reporting module makes supplemental diagnostic informationavailable on additional screens to support the final results. Thesupplemental information allows the operators to further diagnose thecondition of the equipment. In addition, when the condition of thetapblock changes, an e-mail is automatically generated by the reportingmodule 290 and sent to the appropriate plant personnel using apredefined mailing list.

The reporting module 290 draws information, such as temperaturereadings, for example, from the other modules to provide an indicationto the plant personnel of the reason for the e-mail message. Forexample, an e-mail message may be generated whenever the status trafficlight changes color from green to yellow or yellow to red. Automatice-mail generation is a feature of existing programming languages andenvironments developed for the Microsoft Windows operating system. Thereporting module 290 acts as a server, making diagnostic data availableto the user stations 160 over the network connection 150.

FIG. 9 is a block diagram of an alternative embodiment of a diagnosticsystem designated by reference numeral 900. Diagnostic system 900 issimilar to the diagnostic system 100 shown in FIGS. 1 and 2. Thedifference between the two embodiments is that in diagnostic system 900,the data processing functions (performed by modules 250, 260, 270 and290) are divided between a programmable logic controller (PLC) 935 and acomputer system 930, whereas in diagnostic system 100 the dataprocessing functions (250, 260, 270 and 290) are all performed by thediagnostic system 130. PLC 935 is in communication with computer system930 over a dedicated communication link or via network 150.

Dividing the processing functions between the PLC 935 and the computersystem 930 creates a reliable and flexible system. PLC 935 usually has arelatively simple operating system and lacks a hard drive, which in anappropriate application make it less susceptible to errors or failuresthan a personal computer. Typically, once a program is started on a PLC,the program will continue to operate for an extended period, spanningmonths and perhaps years at a time. As a result, having the PLC monitorthe field instruments 125 and provide basic feedback means that themonitoring and feedback can continue even if communication to theremainder of the diagnostic system is lost. The diagnostic computersystem 930, on the other hand, can support more sophisticated programsand is able to store the complete record of the tapblock's 120 operatinglife.

PLC 935 is a computer that performs basic rules-based conditionanalysis. PLC 935 includes a processor 905, an analog to digitalconverter 240, a user interface 915 and may have its own connection tothe network 150. Programs to be executed by the processor 905 may bewritten in a development environment on a personal computer and is thendownloaded onto the PLC 935 directly through a cable connection. Suchprograms are stored in the PLC 935 in non-volatile memory (not shown).

In one embodiment, the field instruments 125, such as thermocouples 210,RTDs 220 and flow meters 230, are directly connected to the PLC 935through special I/O connectors (not shown) on the PLC 935.Alternatively, the field instruments 125 may be connected to the PLC 935via external I/O modules (not shown) that plug into the PLC 935.

Analog field instrument signals received by the PLC 935 are convertedinto digital signals by the analog to digital (A/D) converter 240. TheA/D converter 240 outputs the digital signals to the processor 905 forprocessing. The A/D converter 240 may be an integrated part of the PLC935 or it may be distinct therefrom but coupled thereto.

In the embodiment shown in FIG. 9, processor 905 runs data integritymodule 250 to perform all of the functions of that module, as describedabove in relation to FIG. 2. The processor 905 also sends the processeddata to the diagnostic computer system 930 for further processing. Inthe embodiment shown in FIG. 9, the computer system 930 performs themore computationally complex diagnostic analysis functions and providesa sophisticated display for the operators at user stations 160. Thecomputer system 930 includes a processor 205, a database 280 and amemory unit 208, similar to diagnostic computer system 130. Thediagnostic system 930 can support a more sophisticated operating systemthan that currently available on PLCs. The diagnostic computer system930 may perform all or some of the functions included in the dataprocessing module 260, the diagnostics module 270, and the reportingmodule 290.

In an alternative embodiment (not shown), the processor 905 may also runsoftware to perform some of the functions of the data processing module260 and the diagnostics module 270. Typically, the PLC 935 would notperform any of the functions of the reporting module 290, but it mayprovide a GYR indication independent of status display 140. For example,the processor 905 may generate a GYR status indication that is displayedon status display 940. The status display 940 may be a hard-wired polelight that displays information in a simulated traffic light display orby other visual means.

Exemplary embodiments of the invention are described herein. Certainenhancements or modifications of the described embodiments might be madewithout departing from the spirit and scope of the invention.Accordingly, all such enhancements or modifications, as would beapparent to those skilled in the art, are included within the spirit andscope of the invention.

The invention claimed is:
 1. A diagnostic system for a cooling element of a metallurgical reactor, the system comprising: at least one sensor located in or proximate the cooling element, the at least one sensor configured to sense operating conditions of the cooling element at a plurality of time intervals; at least one processor in communication with the at least one sensor, the at least one processor configured to receive data corresponding to the sensed operating conditions and process the data to determine a relative condition indicator representing accumulated wear of the cooling element, relative to an initial condition of the cooling element, at each time interval over a period of time comprising at least one metallurgical heating and cooling cycle of the cooling element; and at least one display in communication with the at least one processor, the at least one display configured to display the relative condition indicator to a user of the diagnostic system, wherein the at least one sensor comprises at least one optical fiber having temperature-dependent reflection characteristics and the at least one processor comprises a first processor in communication with the at least one sensor and a second processor in communication with the first processor.
 2. The diagnostic system of claim 1, wherein the at least one display comprises a display portion configured to display a first, second or third state representative of the relative condition indicator.
 3. The diagnostic system of claim 1, wherein the at least one sensor comprises a plurality of sensors and further comprises at least one flow sensor for sensing flow of cooling fluid through the cooling element.
 4. The diagnostic system of claim 1, wherein the first processor is comprised in a programmable logic controller.
 5. The diagnostic system of claim 1, wherein the first processor receives the data and the second processor processes the data to determine the relative condition indicator.
 6. The diagnostic system of claim 1, wherein, for each of a plurality of measurement locations, two sensors are used to sense the operating conditions at the respective location.
 7. The diagnostic system of claim 1, wherein the at least one sensor is positioned at least partly within the cooling element.
 8. The diagnostic system of claim 1, wherein the optical fiber comprise a plurality of Bragg gratings.
 9. The diagnostic system of claim 8, wherein the spacing between Bragg gratings is about 10 cm.
 10. The diagnostic system of claim 1, wherein the sensed operating conditions include temperature and coolant flow conditions and wherein the relative condition indicator is determined at least in part by calculating operating parameters indicative of a physical condition of the cooling element based on the data.
 11. The diagnostic system of claim 10, wherein the calculated operating parameters include one or more of a thickness of refractory material within the cooling element and a bonding quality of one or more cooling conduits in the cooling element.
 12. The diagnostic system of claim 1, wherein the at least one processor is configured to process the data to determine whether a fault condition exists in at least one of the sensors.
 13. The diagnostic system of claim 12, wherein the at least one sensor comprises a plurality of sensors and wherein, when the at least one processor determines that a fault condition exists, the at least one processor is configured to determine a reconstructed value for the one sensor based on values of other sensors.
 14. The diagnostic system of claim 1, wherein the at least one display comprises a dedicated display coupled to the at least one processor and located proximate a metallurgical reactor having the cooling element.
 15. The diagnostic system of claim 14, wherein the at least one display further comprises one or more further displays associated with respective one or more remote user stations in communication with the at least one processor over a network.
 16. The diagnostic system of claim 1, wherein the cooling element comprises fluid passages for receiving cooling fluid and some of the plurality of temperature sensors are disposed for sensing temperatures of fluid in the fluid passages and wherein other temperature sensors are disposed for sensing temperatures adjacent a hot face of the cooling element.
 17. The diagnostic system of claim 1, wherein the cooling element is a tapblock.
 18. A diagnostic system for cooling element of a metallurgical reactor, the system comprising: at least one sensor located in or proximate the cooling element, the at least one sensor configured to sense an operating condition of the cooling element at a plurality of time intervals; at least one processor in communication with the at least one sensor, the at least one processor configured to receive data corresponding to the sensed operating conditions and process the data to determine a relative condition indicator representing accumulated wear of the cooling element, relative to an initial condition of the cooling element, at each time interval over a period of time comprising at least one metallurgical heating and cooling cycle of the cooling element; and at least one display in communication with the at least one processor, the at least one display configured to display the relative condition indicator to a user of the diagnostic system, wherein the at least one sensor comprises an optical fiber having temperature-dependent reflection characteristics, wherein the at least one sensor comprises a plurality of sensors and wherein the at least one processor is configured to process data corresponding to the sensed temperature to determine whether a fault condition exists in at least one of the sensors.
 19. A diagnostic method for a cooling element of a metallurgical reactor, comprising: sensing operating conditions of the cooling element relative to an initial condition of the cooling element; receiving data corresponding to the sensed operating conditions; processing the data to determine a relative condition indicator representing accumulated wear of the cooling element, relative to an initial condition of the cooling element, at each time interval over a period of time comprising at least one metallurgical heating and cooling cycle of the cooling element; and displaying the relative condition indicator to a user, wherein sensing is achieved by an optical fiber having temperature-dependent reflection characteristics and the relative condition indicator is determined at least in part by determining an area condition indicator for each of a plurality of areas of the cooling element.
 20. The method of claim 19, wherein the step of displaying includes displaying a first, second or third state representative of the relative condition indicator.
 21. The method of claim 20, wherein the first state corresponds to an operational state of the cooling element, in which the cooling element may be operated normally, the second state corresponds to a cautionary operational state of the cooling element, in which the cooling element should be operated under caution, and the third state corresponds to a non-operational state of the cooling element, in which the cooling element should cease operation or not initiate operation.
 22. The method of claim 19, wherein the relative condition indicator is determined at least in part based on a level and duration of a sensed temperature when the temperature exceeds a predetermined threshold.
 23. The method of claim 19, wherein the relative condition indicator is determined at least in part by the lowest or highest determined area condition indicator.
 24. The method of claim 19, wherein, for each of a plurality of measurement locations, two sensors are used to sense the operating conditions at the respective location.
 25. The method of claim 19, wherein the optical fiber is positioned at least partly within the cooling element.
 26. The method of claim 19, wherein the optical fiber comprises a plurality of Bragg gratings.
 27. The method of claim 19, wherein the relative condition indicator is determined at least in part using principal component analysis of the data.
 28. The method of claim 19, wherein the sensed operating conditions include temperature and coolant flow conditions and wherein the relative condition indicator is determined at least in part by calculating operating parameters indicative of a physical condition of the cooling element based on the data.
 29. The method of claim 28, wherein the calculated operating parameters include one or more of a thickness of refractory material within the cooling element and a bonding quality of one or more cooling conduits in the cooling element. 